Proficiency Testing (PT) Requirements

Field Laboratories

Under the NC WW/GW LC Rule 15A NCAC 2H .0800, laboratories must demonstrate proficiency for all certified parameters (for which a proficiency testing sample is available) each year and the graded results must be received in this office by September 30. Proficiency Testing samples must be obtained from an accredited vendor as unknowns. If performance evaluation samples are not available for a parameter, certification for that parameter may be based on the proper use of the approved procedure as determined by an announced or unannounced on-site inspection.

North Carolina permittees will not be required to order Discharge Monitoring Report-Quality Assurance (DMR-QA) Study PT samples (see DMR-QA PT Study Exemption below). This exemption applies only to DMR-QA Proficiency Testing. All permittees must continue to provide environmental data pursuant to their permit on the monthly discharge monitoring reports. Permittees may order water pollution (WP) PT samples and must have the graded results reported directly to the NC WW/GW LC program. In addition, permittees will not be responsible for reporting data for their contract laboratories any longer. The contract laboratories will analyze PTs for all certified parameters and have data reported directly to the NC WW/GW LC program just as the permittees will do now.

Low-level Total Residual Chlorine PTs

The analysis of proficiency testing (PT) samples is designed to evaluate the entire process used to routinely report environmental analytical results. Therefore, PT samples must be analyzed in the same manner as environmental samples. For example, for colorimetric (i.e., DPD) procedures, Total Residual Chlorine (TRC) PT samples must be analyzed on the same spectrophotometric program (i.e., the sample wavelength) using the same procedure that is used for raw environmental sample analysis. There are two options for achieving this:

If a regular level TRC PT sample is analyzed, it must be diluted to the verified range of the low level curve. The reported result must then be calculated using the dilution factor and the TRC value obtained.

Since the dilution scheme in option 1 may introduce error, it is recommended that the low-level TRC PT sample be analyzed. These are currently available from many approved vendors. This sample should be within the range of your verified curve on the low-level program.

2014 PT Study Requirements

The following links describe proficiency testing requirements for field laboratories. The Proficiency Testing Requirements document serves as a guide to the PT sample requirements of the NC WW/GW LC program. In addition to clarifying the regulatory requirements for proficiency testing, this document answers many common questions concerning evaluation of PT sample results. Also included are important deadlines, penalties and corrective actions for proficiency testing sample failures. Highlighted changes and a condensed version can also be found in the links below.

NOTE: For the first time this year, we have added aqueous and non-aqueous matrices to your certificate attachment. At this time, we will not require PTs specific to each matrix. A single PT in either matrix shall suffice for demonstration of proficiency for that parameter method technology. A specific matrix PT is required only in cases where a method is matrix-specific (e.g., EPA 9071B).

Proficiency Testing Providers

The laboratory must obtain samples that are part of an official study obtained from a proficiency testing sample provider recognized by The NELAC Institute (TNI) and approved by the NC WW/GW LC program. ACLASS and the American Association for Laboratory Accreditation (A2LA) have been designated Proficiency Testing Oversight Bodies (PTOB)/Proficiency Testing Provider Accreditors (PTBA) by TNI. You may see the terms "A2LA-accredited provider" and "NELAC-accredited provider" used interchangeably. In any case, when accessing the list of providers on the websites, select from the "NELAC-accredited" list. Laboratories should check this list each time PT samples are ordered since the list changes periodically.

EPA Lab Codes

Since different accreditation programs use a wide array of laboratory identification systems, the PT providers need a singular means of identifying participant labs when grading and reporting PT results. This singular system of identification is your EPA Lab Code. Each certified laboratory must have an EPA Lab Code and this code must be documented on the results to the proficiency testing provider. Without this EPA Lab Code, the NC WW/GW LC program may be unable to credit the PT results to the correct laboratory. The EPA Lab Codes are assigned by the US EPA. The EPA contact for Lab Code assignment for PT studies is:

DMR-QA PT Study Exemption

In 2008, the NC WW/GW LC program appealed to the US EPA Clean Water Enforcement Branch, Water Protection Division for exemption from the National Pollution Discharge Elimination System (NPDES) DMR-QA PT program. After a thorough review of the NC WW/GW LC program, it was deemed that the NCDENR proficiency testing program provides adequate quality assurance to replace EPA's DMR-QA PT study program. Therefore, all NC dischargers; classified as both Major and Minor, are exempt from the DMR-QA PT Study program as of May 13, 2009. NC dischargers will no longer receive DMR-QA PT study reporting packages from EPA.